The present application is based on Japanese Patent Application No. 2001-8361, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electromagnetic wave shielding structure for connecting multiple shielded wires to a conductive ground member.
2. Related Art
To connect a power feed cable or control signal cable to an arbitrary electric device, including a motor mounted in a vehicle such as an electric car, normally, electromagnetic wave shielding is required. Electromagnetic wave shielding is performed in order to prevent the destabilization of the operation of the electric device due to various types of electrical noise.
A conventional electromagnetic wave shielding structure will now be explained while referring to FIGS. 6 and 7. For this shielding multiple shielded wires 101 are employed. These wires 101 are connected to a conductive ground member 105, such as a motor case, by multiple terminals 102 that are connected to the braided shields of the respective shielded wires 101, and a first holder 103 and a second holder 104 between which the terminals 102 are cramped. By using this arrangement, electromagnetic wave shielding can be provided.
The individual components will now be described. Each shielded wire 101 consists of a core line 106 surrounded by an insulating cover 107 and overlaid by a braided shield (not shown), and an outer cover 108 that encloses the braided shield (see FIG. 7). The shielded wire 101 obtained by the terminal process is employed, and a LAN terminal 109 is connected to the core line 106 through the terminal process. Further, the terminals 102 are connected to the braided shields (not shown).
Each of the terminals 102 includes a main terminal body 110 and a ring member 111, while an annular portion 112 and a braided shield folding portion (not shown) are formed for the main terminal body 110. The annular portion 112 is cramped by the first holder 103 and the second holder 104, and the braided shield (not shown) is folded over the braided shield folding portion (not shown). The ring member 111 is inserted into the outside of the folded over braided shield (not shown), and is caulked at a plurality of positions using a caulking device (not shown).
The fist holder 103, which is conductive, includes: a pair of fixed portions 113, which are securely connected to the grounding member 105; three electric contact portions 114, which have a spring property and which are formed into an arched shape; connecting portions 115, which are located between the fixed portions 113 and the electric contact portions 114; and flat connecting portions 116, which are located between the electric contact portions 114. Bolt through holes 17 are formed in the fixed potions 113 and the connecting portions 115 are formed by bending the fixed portions 113 and the electric contact portions 114, while the connecting portions 116 are formed parallel to the grounding member 105.
The second holder 104, which is conductive, includes: a pair of fixed potions 118, which are lapped over the fixed portions 113 of the first holder 103; three arched pressing portions 119, which press the terminals 102 against the corresponding electric contact portions 114; connecting portions 120, which are formed between the fixed portions 118 and the pressing portions 119; and flat connecting portions 121, which are formed between the pressure portions 119. Further, bolt through holes 123 are formed in the fixed portions 118 for the insertion of the bolts 122, and the pressing portions 119 have a curvature greater than that of the annular portions 112 of the terminals 102.
With this arrangement, the bolts 122 are inserted through the bolt through holes 123 and 117 and engage the grounding member 105. Then, the respective terminals 102 are cramped between the pressing portions 19 and the electric contact portions 114, and the shielded wires 101 are connected to the ground member 105. In this manner, electromagnetic wave shielding is provided.
According to the conventional technique, however, the following four problems with the second holder 104 have arisen.
Since the pressing portions 119 are arched and have a curvature greater than that provided for the annular portions 112 of the terminals 102, when due to a specific factor an external force is applied to the terminals 102 in the direction indicated by an arrow P in FIG. 8, that is, widthwise relative to the terminals 102. The terminals 102, which are held so that they closely contact the electric contact portions 114 by the spring force thereof, may be shifted from their predetermined locations (since each terminal 102 respectively contacts, at only one location each, the electric contact portion 114 and the pressing portion 119, a terminal 102 may be shifted from its predetermined location upon the application of an external force in the direction indicated by the arrow P).
Further, since the pressing portions 119 are simply curved, when due to a specific factor the external force is exerted on the terminals 102 in the direction indicated by an arrow Q in FIG. 9, which is the longitudinal direction of the terminal 102, the terminals 102 may also be shifted in the direction indicated by the arrow Q.
In addition, since the contact load imposed on the terminals 102 and the electric contact portions 114 must be equalized, forming the pressing portion 19 into the arched shape required to press the terminals 102 against the electric contact portions 114 is not easy. As a result, this has an adverse effect on the manufacturing costs.
Furthermore, since a satisfactory rigidity is required to press the terminals 102 against the electric contact portions 114, the thicknesses of the members are increased.
To solve the above shortcomings, it is one objective of the present invention to provide an electromagnetic wave shielding structure that can prevent the shifting of grounding terminals that are cramped between a first holder and a second holder, and that can reduce both the manufacturing costs of a second holder and the weight thereof.
To achieve the above objective, according to a first aspect of the invention, there is provided an electromagnetic wave shielding structure comprising: A shielded wire; a terminal connected to a braided shield of the shielded wire, the terminal is cramped between a first holder and a second holder; the first holder including electric contact portion; the second holder including pressing portion, the pressing portion having a pair of first position regulators and a pair of second position regulators; and a conductive ground member provided so that the shielded wire is connected to the conductive ground member through the terminal and the first holder and the second holder, wherein the electric contact portion contacts the terminal, and the pressing portion presses the terminal against the electric contact portion, and wherein the pair of first regulators contact an outer wall of the terminal in the widthwise direction of the terminal at two places, and a pair of second position regulators contact both ends of the terminal in the longitudinal direction of the terminal.
According to a second aspect of the invention, for the electromagnetic wave shielding structure of the first aspect, the pressing portion is formed in a plate shape.
According to a third aspect of the invention, for the electromagnetic wave shielding structure of the second aspect, a reinforcement rib is formed on the pressing portion.
According to a fourth aspect of the invention, for the electromagnetic wave shielding structure of the first aspect, the pressing portion is provided with a substantially rectangular opening and the pair of first position regulators and the pair of second regulators are formed at edges of the opening.
According to the first aspect of the invention, when the terminals are cramped between the first holder and the second holder, the secured state of the terminals is as follows. A terminal is held at three different positions whereat it is contacted, once each, by either one of the first position regulators or the electric contact portion. Thus, the shifting of the terminal can be satisfactorily prevented when an external force is applied in the widthwise direction. Further, since the terminal is positioned so that at both ends it is secured to one of the regulators of the second position regulator pair, the shifting of the terminal can also be satisfactorily prevented when an external force is applied in the longitudinal direction.
According to the second aspect of the invention, since the pressing portions are flat plates, the manufacturing of the second holder is improved. And furthermore, according to the third aspect of the invention, since the pressing portions include reinforcement ribs, the rigidity of the second holder can be maintained even when the weight of the second holder is reduced.